HEAT oven to 375°F.
MIX first 5 ingredients. Beat butter, sugars and peanut butter in large bowl with mixer until light and fluffy. Add egg and vanilla; mix well. Gradually beat in flour mixture. Add chocolate; mix well.
DROP heaping tablespoonfuls of dough, 2 inches apart, onto baking sheets.
BAKE 10 to 12 min. or until lightly browned. Cool 1 min.; remove from baking sheets to wire racks. Cool completely.
serving size = 1 cookie (28 g)